I've been wondering this for a while now, and finally...

[shox75]

remembered to ask you guys.
What is that round plastic thing that kinda looks like a wastegate or diaphragm out of the left side top of the intake manifold when looking from the front of vehicle. (stock 1.6 TD)

it is kinda hidden under the intake pipe and it has a flat head adjustment screw at the top of it. Also has a dummy male side connector, with nothing plugged into it.

Is anything adjusted from this?

[vwmike]

That's just a pop valve that opens up if boost goes past it's opening point so it can "protect" the engine.

[steve]

I think you could perhaps crank it down and up the pressure at which it pops....